KENNEDY SPACE CENTER - During the space shuttle's last flight three summers ago visitors crammed the NASA Causeway to glimpse a final, majestic launch. But this June, as sunshine dappled the waters below, the bridge stood nearly empty.

As NASA considers what company will build a replacement for the space shuttle, which the space agency needs to transport its astronauts to the International Space Station and end an uncomfortable dependence upon Russia, one of the three competitors is offering more than just a spacecraft.

Boeing has put jobs on the table, too, saying it will build its CST-100 spacecraft at NASA's Florida space center, where the launch crowds could return as soon as 2017.

Boeing's insider style differs markedly from that of another competitor, SpaceX, an upstart that has taken an outsider's approach, preferring to build its spacecraft in-house. The final bidder, Sierra Nevada, is somewhere in between.

NASA should make its decision on the "commercial crew" competition in the next few weeks. At stake is not just a $4 billion contract, but prestige. The next spacecraft that flies U.S. astronauts will have an American flag, yes, but also a prominent corporate logo. That company will also join the elite club - whose only members include the United States, Russia and China - that has flown humans in space.

When Boeing brought a mock-up of its CST-100 to Kennedy Space Center in June, Boeing chose a setting both symbolic and pragmatic for a blue-blooded NASA contractor.

"It's just really great to be back here," said John Elbon, head of Boeing's space divison, standing on a platform inside the Orbiter Processing Facility. To his right was the CST-100 spacecraft. To his left sat Florida Senator Bill Nelson, a former astronaut who wields considerable influence over NASA.

Nelson was all smiles at the prospect of returning manned spacecraft launches and 300 jobs to the sunshine state. "This is the celebration of a great public-private partnership," he said.

The partnership goes back more than half a century. Beginning with Project Mercury, America's first manned orbital spacecraft, Boeing has served as lead contractor in most of NASA's human spaceflight endeavors. Today it has the contract to sustain the International Space Station and is building NASA's next rocket, the large Space Launch System.

Not only is Boeing offering incentives in Florida, it's doing so in Houston as well. The shuttle's retirement also battered Johnson Space Center. Without regular flights to manage, mission control has shed 40 percent of its workforce, or more than 1,300 jobs. Boeing has contracted to use mission control to manage CST-100 flights.

Elbon said the company has emphasized safety and reliability in its design and development of the spacecraft.

The CST-100's shape, mimicking the Apollo capsule, is proven. Its flight computers are the same as those in Boeing's proven X-37 unmanned space plane. Many of its other systems have previously flown in space. The spacecraft will launch into orbit on the Atlas V rocket, which has made four dozen successful flights.

"We go for substance," Elbon said. "Not pizazz."

A reusable capsule

He was referring to SpaceX and, both on and off the record, a lot of people in the aerospace make such allusions. That's because SpaceX has captured the public's imagination and shaken up the spaceflight community with its low-cost rockets.

And the California-based company is flashy, like its chief executive Elon Musk, a dot-com entrepreneur with a rock star persona who helped found Paypal and also heads Tesla Motors, the electric car manufacturer.

A month before Boeing's event in Florida to showcase the CST-100, SpaceX held its own affair to reveal the Dragon V2, its entrant into the competition.

SpaceX unveiled the capsule at its California headquarters as multi-colored lights flashed and smoke swirled.

And there was Musk, a master showman, working the crowd. Wearing a sport coat with the top two buttons undone on his collared shirt, Musk explained that the Dragon V2 would be the first reusable capsule and, with thrusters, could land up to seven astronauts almost anywhere they liked on Earth. No more thudding to the ground on a predetermined course.

"That is how a 21st century spaceship should land," Musk said.

It was classic Musk: boasting and proud before an audience of employees, guests and invited journalists. Building a reusable capsule, never before done, may prove difficult to back up.

But by building in-house, and pressing employees to work long hours, there's no question SpaceX is cutting the cost of access to space and shaking up the establishment.

The Air Force recently awarded a contract for dozens of security satellite launches to United Launch Alliance, a joint venture between Boeing and Lockheed Martin, which flies the Atlas V rocket. The Air Force did so on a non-competitive basis, saying Musk's Falcon 9 rocket wasn't certified. But Musk, whose Falcon 9 rocket is three to four times cheaper, said the contract should be re-competed and has sued.

Sierra Nevada

If SpaceX is the unqualified outsider to Boeing's consummate insider, Sierra Nevada, based outside Denver in Louisville, Colo., lies somewhere in the middle.

While it's no Boeing, Sierra Nevada is probably the biggest aerospace company most Americans have never heard of. Privately held, with $2 billion in annual revenues, Sierra Nevada builds spacecraft motors, propulsion systems and is the largest small satellite builder in the world.

"It surprises people because often times, if they don't know me or us, they come in thinking maybe these guys make beer or something," said Mark Sirangelo, Corporate Vice President of SNC Space Systems. "The truth is we know what we're doing and this isn't a new game for us."

In 2005, five years before NASA awarded its first contracts to private companies, Sierra Nevada began work on its vehicle, the Dream Chaser.

"We made an audacious bet, that some day America was going to need an updated version of the space shuttle," Sirangelo said.

The company found the answer in an old NASA design, the HL-20 space plane the agency worked on in the 1990s but never actually built. Sierra Nevada kept the vehicle's shape, but reworked the vehicle's engine and made room inside for up to seven astronauts.

The Dream Chaser lands like an airplane, on the same sized runway that 737 jets do. It can also fly around in space and, for example, take astronauts up to the Hubble Space Telescope for repairs.

Like Boeing, Sierra Nevada is working with NASA to develop the vehicle and has contracts with most of NASA's field centers for work.

Yet Sierra Nevada is similar to SpaceX in some ways. Both companies are investing heavily in their vehicles. Sirangelo said, "we are nearly putting in dollar for dollar" for development money received so far from NASA. Like SpaceX and the DragonV2, Sierra Nevada also plans to continue developing Dream Chaser, albeit at a slower rate, if it fails to win a new NASA contract.

Boeing could lay off 215

Boeing will not say how much of its own money has been invested in its CST-100. The large aerospace contractor also says it won't continue developing the CST-100 if it loses the commercial crew contract. The company has notified 170 employees in Houston and 45 in Florida that they would be laid off in the event of a loss.

NASA hopes to support two companies moving forward, to have multiple ways to space. However, due to funding, the space agency may only be able to pick one winner, or perhaps one winner and a partial award to a second company.

Although the commercial crew idea originated during the administration of George W. Bush, President Obama endorsed it as the quickest and cheapest means of ending American reliance on Russia.

Yet as the president sought to privatize parts of NASA, Congress objected and underfunded the program. Perhaps mindful of its home districts and states, Congress was reticent to divert money from NASA's other programs.

This attitude has softened in recent months, however, as the Ukraine crisis has lain bare NASA's reliance upon Russia for access to space.